Milk ejection is due to which hormone -

Ans. is 'a' i.e., Oxytocin Physiology of Lactation* 500-800 ml of milk is produced by a healthy mother per day which requires 700 kcal/day.* Physiological basis consists of 4 phases:1. Mammogenesis : Growth of both ductal and lobuloalveolar systems occurs in pregnancy2. Lactogenesis : Colostrum secretion is noted during pregnancy and immediately post delivery. Milk secretion starts around the third postpartum day. Despite high prolactin levels in pregnancy, milk is not secreted as the high levels of estrogen and progesterone make the breast tissue unresponsive. With withdrawal of estrogen and progesterone levels post delivery, prolactin acts on the breast tissue. Growth hormone, thyroxine and insulin also increase secretory activity.3. Galactokinesis: Milk is discharged due to the infant's suckling efforts and also a contractile mechanism which expresses milk from the alveoli into the ducts. Oxytocin is a major galactokinetic hormone.# Milk ejection reflex: Reflex by which milk is forced down into the ampulla of the lactiferous duct, where it can be sucked out by the baby.4. Galactopoeisis : The most important hormone is prolactin. Suckling is essential for effective and continuous lactation. Periodic feeding is essential to relieve the pressure which then maintains the secretion.